Apparatus and method for starting engine of mild hybrid electric vehicle

ABSTRACT

An apparatus for starting engine of mild hybrid electric vehicle may include: an ignition switch; an ambient temperature detector; a state of charge (SOC) detector; a mild starter &amp; generator (MHSG) including a stator and a rotor mounted inside the stator; a starter which is configured to start the engine independently of the MHSG; a converter which is configured to voltage-drop an electric power of a high voltage battery and supply it to the low voltage battery or the starter; an MHSG wheel rotating integrally with the rotor; an MHSG position detector; and a controller configured for determining a top dead center (TDC) of a predetermined cylinder based on a signal of the MHSG position detector.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2017-0174100 filed on Dec. 18, 2017, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an apparatus and method for startingengine of mild hybrid electric vehicle.

Description of Related Art

In general, a hybrid electric vehicle utilizes an internal combustionengine and a battery power source together. The hybrid electric vehicleefficiently combines a torque of the internal combustion engine and atorque of a motor.

Hybrid electric vehicles may be divided into a hard type and a mild typeaccording to power-sharing ratio between an engine and a motor. In thecase of the mild type of hybrid electric vehicle (hereinafter referredto as a mild hybrid electric vehicle), a mild hybrid starter & generator(MHSG) configured to start the engine or generate electricity accordingto an output of the engine is used instead of an alternator. In the caseof the hard type of hybrid electric vehicle, a driving motor configuredfor generating driving torque is used in addition to an integratedstarter & generator (ISG) configured to start the engine or generateelectricity.

The MHSG may assist torque of the engine according to running states ofthe vehicle and may charge a battery (e.g., 48 V battery) throughregenerative braking. Accordingly, fuel efficiency of the mild hybridelectric vehicle may be improved.

The mild hybrid electric vehicle may include a starter and the MHSG usedas motors for starting the engine. When the engine is started by thestarter in a very cold weather, there has been a problem in that a timerequired to start the engine is increased or starting the engine becomesimpossible because of the battery discharge.

The information included in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and may not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing anapparatus and method for starting engine of mild hybrid electric vehiclehaving advantages of improving startability of the engine when ambienttemperature is low.

An apparatus configured for starting engine of mild hybrid electricvehicle according to an exemplary embodiment of the present inventionmay include: an ignition switch including a plurality of contact points;an ambient temperature detector configured for detecting an ambienttemperature of the mild hybrid electric vehicle; a state of charge (SOC)detector configured for detecting a state of charge (SOC) value of a lowvoltage battery; a mild starter & generator (MHSG) including a statorand a rotor disposed inside the stator, and starting an engine orgenerating electricity according to an output of the engine; a starterwhich is able to start the engine independently of the MHSG; a converterwhich is able to voltage-drop an electric power of a high voltagebattery and supply it to the low voltage battery or the starter; a mildhybrid starter & generator (MHSG) wheel rotating integrally with therotor; a mild hybrid starter & generator (MHSG) position detectorconfigured for detecting position of the MHSG; and a controllerconfigured for determining a top dead center (TDC) of a predeterminedcylinder according to a signal of the MHSG position detector, whereinthe controller is configured to operate the starter to start the enginewhen the ambient temperature is less than a predetermined temperatureand the SOC value of the low voltage battery is less than apredetermined SOC.

When the ambient temperature is less than the predetermined temperatureand the SOC value of the low voltage battery is less than thepredetermined SOC, the controller may voltage-drop the electric power ofthe high voltage battery by the converter, and may operate the starterto start the engine with the voltage-dropped electric power of the highvoltage battery and the electric power of the low voltage battery.

Before operating the starter to start the engine, the controller mayoperate the MHSG so that a position of a camshaft of the enginecorresponds to a predetermined position.

When the ambient temperature is equal to or greater than thepredetermined temperature, the controller may operate the starter tostart the engine with the electric power of the low voltage battery.

When the ambient temperature is less than the predetermined temperatureand the SOC value of the low voltage battery is equal to or greater thanthe predetermined SOC, the controller may operate the starter to startthe engine with the electric power of the low voltage battery.

The MHSG wheel may have at least three teeth on a circumference thereof,and sizes of the at least three teeth and intervals between them may bedifferent from each other.

The at least three teeth may include a first tooth, a second tooth and athird tooth, a distance between a positive flank and a negative flank ofthe first tooth, a distance between a positive flank and a negativeflank of the second tooth, and a distance between a positive flank and anegative flank of the third tooth may be different from each other, anda distance between the negative flank of the first tooth and thepositive flank of the second tooth, a distance between the negativeflank of the second tooth and the positive flank of the third tooth, anda distance between the negative flank of the third tooth and thepositive flank of the first tooth may be different from each other.

A hole may be formed at a center portion of the MHSG wheel and arotation shaft of the rotor may penetrate the hole.

The MHSG may be operated with the electric power of the high voltagebattery.

A method for starting engine of mild hybrid electric vehicle accordingto an exemplary embodiment of the present invention may include:comparing an ambient temperature with a predetermined temperature;comparing a state of charge (SOC) value of a low voltage batterydetected by an SOC detector with a predetermined SOC when the ambienttemperature is less than the predetermined temperature; and operating,by a controller, a starter which is able to start an engine, to startthe engine when the SOC value of the low voltage battery is less thanthe predetermined SOC.

The method may further include; when the ambient temperature is lessthan the predetermined temperature and the SOC value of the low voltagebattery is less than the predetermined SOC, voltage-dropping an electricpower of the high voltage battery by the converter; supplying thevoltage-dropped electric power of the high voltage battery and theelectric power of the low voltage battery to the starter; and operatingthe starter to start the engine.

The method may further include, before operating the starter to startthe engine, operating, by the controller, the MHSG so that a position ofa camshaft of the engine corresponds to a predetermined position.

The method may further include, when the ambient temperature is equal toor greater than the predetermined temperature, operating, by thecontroller, the starter to start the engine with the electric power ofthe low voltage battery.

The method may further include, when the ambient temperature is lessthan the predetermined temperature and the SOC value of the low voltagebattery is equal to or greater than the predetermined SOC, operating, bythe controller, the starter to start the engine with the electric powerof the low voltage battery.

According to an exemplary embodiment of the present invention, a starteris operated with simultaneously applied electric power of high voltagebattery and low voltage battery when ambient temperature is very low,improving startability of an engine.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a mild hybrid electric vehicleaccording to an exemplary embodiment of the present invention.

FIG. 2 is an exploded perspective view of a mild hybrid starter &generator (MHSG) according to an exemplary embodiment of the presentinvention.

FIG. 3 is a cross-sectional view of a mild hybrid starter & generator(MHSG) wheel according to an exemplary embodiment of the presentinvention.

FIG. 4 is a view exemplarily illustrating an apparatus configured forstarting an engine of a mild hybrid electric vehicle according to anexemplary embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method for starting an engine of amild hybrid electric vehicle according to an exemplary embodiment of thepresent invention.

It may be understood that the appended drawings are not necessarily toscale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the present invention.The specific design features of the present invention as includedherein, including, for example, specific dimensions, orientations,locations, and shapes will be determined in part by the particularlyintended application and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the presentinvention(s) will be described in conjunction with exemplary embodimentsof the present invention, it will be understood that the presentdescription is not intended to limit the present invention(s) to thoseexemplary embodiments. On the other hand, the present invention(s)is/are intended to cover not only the exemplary embodiments of thepresent invention, but also various alternatives, modifications,equivalents and other embodiments, which may be included within thespirit and scope of the present invention as defined by the appendedclaims.

In the following detailed description, various Exemplary embodiments ofthe present application will be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of the presentinvention are shown. However, the present invention is not limited theexemplary embodiments which are described herein, and may be modified invarious different ways.

Parts which are not related with the description are omitted for clearlydescribing the exemplary embodiment of the present invention, and likereference numerals refer to like or similar elements throughout thespecification.

Since each component in the drawings is arbitrarily illustrated for easydescription, the present invention is not limited to the componentsillustrated in the drawings.

FIG. 1 is a schematic diagram of a mild hybrid electric vehicleaccording to an exemplary embodiment of the present invention.

As shown in FIG. 1, a mild hybrid electric vehicle according to anexemplary embodiment of the present invention includes an engine 10, atransmission 20, a mild hybrid starter & generator (MHSG) 30, a starter40, a high voltage battery 50, a low voltage battery 52, converter 54, adifferential gear apparatus 60, and a wheel 65.

The engine 10 combusts fuel and air to convert chemical energy intomechanical energy. Ignition timing, an air amount, a fuel amount, and anair-fuel ratio may be controlled to generate combustion torque of theengine 10.

In connection with torque transmission of the mild hybrid electricvehicle, torque generated from the engine 10 is transmitted to an inputshaft of the transmission 20, and a torque output from an output shaftof the transmission 20 is transmitted to an axle via the differentialgear apparatus 60. The axle rotates the wheel 60 so that the mild hybridelectric vehicle runs by the torque generated from the engine 10.

The transmission 20 may be an automatic transmission or a manualtransmission. The automatic transmission controls hydraulic pressure byoperating a plurality of solenoid valves based on a speed of the mildhybrid electric vehicle and a position of an accelerator pedal, so thata shift gear of a target gear stage is operated and shifting isautomatically performed. In the case of the manual transmission,shifting is performed as a driver steps on a clutch pedal and moves agear lever to a desired gear stage.

The MHSG 30 converts electrical energy into mechanical energy orconverts the mechanical energy into the electrical energy. In otherwords, the MHSG 30 starts the engine 10 or generates electricityaccording to an output of the engine 10. Furthermore, the MHSG 30 mayassist the torque of the engine 10. The torque of the engine 10 may beused as main torque, and a torque of the MHSG 30 may be used asauxiliary torque. The MHSG 30 may be connected to a crankshaft 12 and acamshaft 14 of the engine 10 through a belt 32.

The starter 40 starts the engine 10. The starter 40 may be directlyconnected to the crankshaft 12 of the engine 10.

The high voltage battery 50 may supply electricity to the MHSG 30, andmay be charged through electricity recovered by the MHSG 30. The highvoltage battery 50 may be a lithium-ion battery having 48 V voltage, butthe present invention is not limited thereto.

The low voltage battery 52 may supply a low voltage current toelectrical loads (e.g., a headlamp and an air conditioner) or thestarter 40. The low voltage battery 52 may be a 12 V battery.

The converter 54 may be a DC-DC converter which converts a voltagesupplied form the high voltage battery 50 into a low voltage and supplyit to the low voltage battery 52. The low voltage battery 52 may becharged by the electric power supplied from the high voltage battery 50.

FIG. 2 is an exploded perspective view of a mild hybrid starter &generator (MHSG) according to an exemplary embodiment of the presentinvention, and FIG. 3 is a cross-sectional view of a mild hybrid starter& generator (MHSG) wheel according to an exemplary embodiment of thepresent invention.

Referring to FIG. 2 and FIG. 3, a mild hybrid starter & generator (MHSG)30 according to an exemplary embodiment of the present invention mayinclude a rotor 31, a stator 32, a first case 33 a, a second case 33 b,a third case 33 c, a power module 34, a control module 35, a mild hybridstarter & generator (MHSG) wheel 300, and a mild hybrid starter &generator (MHSG) position detector 96.

A rotation shaft 31 a is coupled to a center portion of the rotor 31,and the rotor 31 is disposed inside the stator 32 so that an externalcircumference of the rotor 31 is distanced from an internalcircumference of the stator 32 by a predetermined interval. The rotor 31is rotatable disposed inside the stator 32.

The stator 32 includes a stator core 32 a including an electric steelplate and a coil 32 b wound around the stator core 32 a. The coil 32 bis electrically connected to the power module 34 to receive a currentfrom the power module 34. When the current applied to the coil 32 b fromthe power module 34, the rotator 31 is rotated by flux, and the MHSG 30generates torque.

The first case 33 a and the second case 33 b are coupled to form a spacein which the rotor 31 and the stator 32 may be disposed. The stator 32may be fixed inside the second case 33 b.

The second case 33 b and the third case 33 c are coupled to form a spacein which the power module 34 and the control module 35 may be disposed.The power module 34 and the control module 35 may be fixed inside thethird case 33 c.

The power module 34 applies the current to the coil 32 b of the stator32 according to a control signal of the control module 35.

The control module 35 controls operation of the power module 34according to a control signal of a controller 80 (refer to FIG. 4) andcontrols the current applied to the coil 32 b of the stator 32.Furthermore, the control module 35 receives a signal of the MHSGposition detector 96 and transmits a signal corresponding thereto to thecontroller 80.

The MHSG wheel 300 rotates integrally with the rotor 31. A hole 340 isformed at a center portion of the MHSG wheel 300, and the rotation shaft31 a of the rotor 31 may be fixed to penetrate the hole 340. At leastthree teeth 310, 320 and 330 are formed on a circumference of the MHSGwheel 300. Sizes of the plurality of teeth 310, 320 and 330 and theintervals between them may be different from each other.

Each of the at least three teeth 310, 320 and 330 includes a positiveflank and a negative flank. Herein, the positive flank is a portionwhere a tooth starts along a rotation direction of the MHSG wheel 300,and the negative flank is a portion where a tooth end portions along therotation direction of the MHSG wheel 300.

A distance b′ between a positive flank 312 and a negative flank 314 ofthe first tooth 310, a distance d′ between a positive flank 322 and anegative flank 324 of the second tooth 320, and a distance f between apositive flank 332 and a negative flank 334 of the third tooth 330 maybe different from each other. Furthermore, a distance between c′ thenegative flank 314 of the first tooth 310 and the positive flank 322 ofthe second tooth 320, a distance e′ between the negative flank 324 ofthe second tooth 320 and the positive flank 332 of the third tooth 330,and a distance a′ between the negative flank 334 of the third tooth 330and the positive flank 312 of the first tooth 310 may be different fromeach other.

The MHSG position detector 96 detects positions of the at least threeteeth 310, 320 and 330 (i.e., a position of the MHSG wheel 300), andtransmits a signal corresponding thereto to the control module 35. TheMHSG position detector 96 may be fixedly disposed at the power module34.

FIG. 4 is a view exemplarily illustrating an apparatus configured forstarting an engine of a mild hybrid electric vehicle according to anexemplary embodiment of the present invention.

As shown in FIG. 4, an apparatus configured for starting an engineaccording to an exemplary embodiment of the present invention mayinclude an ignition switch 72, an ambient temperature detector 74, anSOC detector 76, the MHSG wheel 300, the MHSG position detector 96, thecontroller 80, the MHSG 30, and a starter 40.

The ignition switch 72 may include a plurality of contact points. Theplurality of contact points may include an OFF contact point, an ACCcontact point, an ON contact point, and a START contact point. When theOFF contact point is selected, the engine is turned off. When the ACCcontact point is selected, accessory devices such as a radio may beused. When the ON contact point is selected, electronic devices using avoltage of the battery 50 may be used. When the START contact point isselected, the engine 10 is started. Contact points of the ignitionswitch 72 may be selected by a starting key or a starting button.

The ambient temperature detector 74 detects an ambient temperature ofthe mild hybrid electric vehicle, and transmits a signal correspondingthereto to the controller 80.

The SOC detector 76 detects a state of charge (SOC) value of the battery50, and transmits a signal corresponding thereto to the controller 80.

A crankshaft wheel 100 is mounted to the crankshaft 12 of the engine 10so that it integrally rotates with the crankshaft 12, and a plurality ofteeth 110 are formed on a circumference of the crankshaft wheel 100.Sizes and intervals of the plurality of teeth 110 are the same, and aguide groove 115 is formed on a portion of the crankshaft wheel 100 todetect a reference position of the crankshaft 12.

The crankshaft position detector 92 detects positions of the pluralityof teeth 110 (i.e., a position of the crankshaft 12), and transmits asignal corresponding thereto to the controller 80. The controller 80 maydetermine a rotation speed of the engine 10 based on the signal of thecrankshaft position detector 92.

A camshaft wheel 200 is mounted to the camshaft 14 of the engine 10 sothat it integrally rotates with the camshaft 14, and a plurality ofteeth 210, 220 and 230 with non-uniform interval are formed on acircumference of the camshaft wheel 200. Sizes of the plurality of teeth210, 220 and 230 and the intervals between them may be different fromeach other.

The camshaft position detector 94 detects positions of teeth 210, 220and 230 (i.e., a position of the camshaft 14), and transmits a signalcorresponding thereto to the controller 80. The controller 80 may detecta top dead center (TDC) of a predetermined cylinder 16 based on thesignal of the camshaft position detector 94. In a case of afour-cylinder engine, the predetermined cylinder 16 may be a firstcylinder, and the camshaft 14 may rotate once when the crankshaft 12rotates twice.

The MHSG wheel 300 is mounted to the MHSG 30 so that it integrallyrotates with the MHSG 30, and at least three teeth 310, 320 and 330 areformed on the circumference of the MHSG 30. Sizes of the plurality ofteeth 310, 320 and 330 and the intervals between them may be differentfrom each other. Furthermore, intervals of the teeth 310, 320 and 330 ofthe MHSG wheel 300 are the same as the teeth 210, 220 and 230 of thecamshaft wheel by a predetermined angle difference (x3-x2).

The MHSG position detector 96 detects positions of the at least threeteeth 310, 320 and 330 (i.e., a position of the MHSG wheel 300), andtransmits a signal corresponding thereto to the control module 35. Thecontrol module 35 transmits the signal to the controller 80. Thecontroller 80 may detect a top dead center (TDC) of the predeterminedcylinder 16 based on the signal of the MHSG position detector 96.

The controller 80 may control operation of the MHSG 30 based on thesignals of the crankshaft position detector 92, the camshaft positiondetector 94, and the MHSG position detector 96. Furthermore, thecontroller 80 may control operations of the MHSG 30 and the starter 40based on the signals of the ignition switch 72, the ambient temperaturedetector 74, and the SOC detector 76. The controller 80 may beimplemented with one or more processors executed by a predeterminedprogram, and the predetermined program may include a series of commandsfor performing each step included in a method for starting an engine ofa mild hybrid electric vehicle according to an exemplary embodiment ofthe present invention to be described below.

Hereinafter, a method for starting engine of a mild hybrid electricvehicle according to an exemplary embodiment of the present inventionwill be described in detail with reference to FIGS. 2 to 5.

FIG. 5 is a flowchart illustrating a method for starting engine of amild hybrid electric vehicle according to an exemplary embodiment of thepresent invention.

Referring to FIGS. 2 to 5, the controller 80 determines whether theSTART contact point of the ignition switch 72 is selected at step S100.

When the START contact point of the ignition switch 72 is not selectedat step S100, the controller 80 finishes the method for starting theengine of the mild hybrid electric vehicle according to an exemplaryembodiment of the present invention.

When the START contact point of the ignition switch 72 is selected atstep S100, the controller 80 compares the ambient temperature with apredetermined temperature at step S110. The predetermined temperaturemay be determined by a person of ordinary skill in the art to determinewhether a cold-start condition of the engine 10 is satisfied. Forexample, the predetermined temperature may be −20° C.

When the ambient temperature is equal to or greater than thepredetermined temperature at step S110, the controller 80 operates thestarter 30 to start the engine 10 with the electric power of the lowvoltage battery at step S120.

When the ambient temperature is less than the predetermined temperatureat step S110, the controller 80 compares the SOC value of the lowvoltage battery 52 with a predetermined SOC at step S130. Thepredetermined SOC may be determined by a person of ordinary skill in theart to determine whether the low voltage battery 52 may be fullydischarged.

When the SOC value of the low voltage battery 52 is equal to or greaterthan the predetermined SOC at step S130, the controller 80 operates thestarter 40 to start the engine 10 with the electric power of the lowvoltage battery 52 at step S120. In other words, when the low voltagebattery 52 is in a state sufficient to operate the starter 40 to startthe engine 10 even under the cold-start condition, the controller 80 maymake the starter 40 be operated only with the electric power of the lowvoltage battery 52.

When the SOC value of the low voltage battery 52 is less than thepredetermined SOC at step S130, the controller 80 operates the MHSG 30so that the position of the camshaft 14 of the engine 10 becomes apredetermined position at step S140. The predetermined position may bedetermined by a person of ordinary skill in the art in consideration ofefficiency of starting and combustion safety. Because the position ofthe camshaft 14 exists at the predetermined position when starting theengine 10, fuel injection may be started from a specific cylinder,starting the engine 10 without a delay time.

In an exemplary embodiment of the present invention, the converter 54may be connected to the controller 80.

When the position of the camshaft 14 becomes the predetermined position,the converter 54 connected to the controller 80 voltage-drops theelectric power of the high voltage battery 50 at S150, and thecontroller 80 supplies it with the electric power of the low voltagebattery 52 to the starter 40 simultaneously at S160. Therefore, thestarter 40 is operated with the voltage-dropped electric power of thehigh voltage battery 50 and the electric power of the low voltagebattery 52 to start the engine 10 at S170. Accordingly, startability ofthe engine 10 may be improved when ambient temperature is very low.

As described above, according to an exemplary embodiment of the presentinvention, startability of the engine 10 may be improved in a very coldweather.

For convenience in explanation and accurate definition in the appendedclaims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”,“upper”, “lower”, “upwards”, “downwards”, “front”, “rear”, “back”,“inside”, “outside”, “inwardly”, “outwardly”, “internal”, “external”,“inner”, “outer”, “forwards”, and “backwards” are used to describefeatures of the exemplary embodiments with reference to the positions ofsuch features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit thepresent invention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described toexplain certain principles of the present invention and their practicalapplication, to enable others skilled in the art to make and utilizevarious exemplary embodiments of the present invention, as well asvarious alternatives and modifications thereof. It is intended that thescope of the present invention be defined by the Claims appended heretoand their equivalents.

1-10. (canceled)
 11. A method for starting an engine of a mild hybridelectric vehicle, the method comprising: comparing, by a controller, anambient temperature with a predetermined temperature; comparing, by thecontroller, a state of charge (SOC) value of a low voltage batterydetected by an SOC detector with a predetermined SOC; and operating, bythe controller, a starter which is configured to start the engine, tostart the engine according to a result of comparing the ambienttemperature with the predetermined temperature and of comparing the SOCvalue of the low voltage battery with the predetermined SOC.
 12. Themethod of claim 11, wherein the controller is configured to operate thestarter to start the engine when the ambient temperature is less thanthe predetermined temperature and the SOC value of the low voltagebattery is less than the predetermined SOC.
 13. The method of claim 12,further including: when the ambient temperature is less than thepredetermined temperature and the SOC value of the low voltage batteryis less than the predetermined SOC, voltage-dropping, by a converter, anelectric power of the high voltage battery; supplying thevoltage-dropped electric power of the high voltage battery and anelectric power of the low voltage battery to the starter; and operatingthe starter to start the engine.
 14. The method of claim 11, furtherincluding: before operating the starter to start the engine, operating,by the controller, a mild starter & generator (MHSG) so that a positionof a camshaft of the engine corresponds to a predetermined position. 15.The method of claim 11, further including: when the ambient temperatureis equal to or greater than the predetermined temperature, operating, bythe controller, the starter to start the engine with an electric powerof the low voltage battery.
 16. The method of claim 11, furtherincluding: when the ambient temperature is less than the predeterminedtemperature and the SOC value of the low voltage battery is equal to orgreater than the predetermined SOC, operating, by the controller, thestarter to start the engine with an electric power of the low voltagebattery.
 17. The method of claim 14, wherein the MHSG includes a statorand a rotor mounted inside the stator, and configured for starting theengine or generating electricity by an output of the engine, and whereinan MHSG wheel is connected to the rotor and rotates integrally with therotor.
 18. The method of claim 17, wherein the MHSG wheel has at leastthree teeth on a circumference thereof, and sizes of the at least threeteeth and intervals between two of the at least three teeth aredifferent from each other.
 19. The apparatus of claim 18, wherein the atleast three teeth include a first tooth, a second tooth and a thirdtooth, wherein a distance between a positive flank and a negative flankof the first tooth, a distance between a positive flank and a negativeflank of the second tooth, and a distance between a positive flank and anegative flank of the third tooth are different from each other, andwherein a distance between the negative flank of the first tooth and thepositive flank of the second tooth, a distance between the negativeflank of the second tooth and the positive flank of the third tooth, anda distance between the negative flank of the third tooth and thepositive flank of the first tooth are different from each other.